This invention relates to an optical fiber cable for easily identifying a specific cable among a number of laid cables, a method for manufacturing the optical fiber cable and facilities used for the method.
For example, numerous optical fiber cables are laid in a trough. Central offices are disposed at intervals of 2.5 to 5 km. The numerous cables are terminated at main distribution frames in each central office. It is required to surely identify each cable when managing the cables terminated at the main distribution frames and removing one or some of the cables.
A conventional related cable identification method is that identification markings are marked on a sheath surface of each cable, or that at least one identification tag is attached to a tail end of each cable. The identification markings have cable information, such as the name of a manufacturer, the date of manufacture, a cable product name, and the cable length, being marked on the cable surface by ink, heat embossing, a laser beam or the like. The identification tag has, for example, cable information on the items as mentioned above, being marked on a thin metal plate to be attached to each cable, or being bound by a metal wire or wires or the like (e.g., refer to Japanese Patent Laid-Open No. Hei 6(1994)-60750).
According to another conventional cable identification method, laying-related information for an optical cable is converted into a 2-dimensional QR (Quick Response) code to be printed on the QR code printed paper, which is attached to the sheath of the optical cable. During maintenance, a code reader scans the QR code printed paper to read the recorded information at a laying site. The QR code printed paper has the optical cable information to be read out, similarly in place of a barcode, a magnetic card or an IC card (e.g., refer to Japanese Patent Laid-Open No. 2001-21730).
However, each of these cable identification methods suffers from deficiencies that reduce their effectiveness.
In the aforementioned identification method, the identification markings are marked on the surface of the cable in a longitudinal direction of the cable. Accordingly, as the number of characters and numerals in the identification markings increase, the longer section of cable, buried in a trough or in the ground, is needed to mark the identification markings. Removal of a trough cover or of soil and sand over a long section increases construction costs. Therefore, the entire length of the identification markings is should be 1 m or less. However, if the number of characters and numerals is limited to be marked in about 1 m, it is not realistic to mark all of the necessary information.
Additionally, the identification markings are subject to degrade illegibly due to aging effects or due to abrasion.
Further, if identification tags are used, they are required to be attached to a laid cable at regular intervals. Accordingly, the number of tags becomes enormous, increasing construction costs.
Moreover, as there is a limit to the number of characters and numerals marked on the identification tag, it is not realistic to mark all of the necessary information. The identification tag has characters and numerals marked thereon by embossing or the like. As well as the identification markings, the characters and numerals may be illegible due to aging effects or due to abrasion.
Still further, if the QR code printed paper or the like is used, attached to the sheath of the optical cable, it has less written information that the alternative methods, and can also be degraded due to aging effects or due to abrasion.
Cable identification is required to determine a specific cable among numerous cables during cable replacement work or removal work. However, if identification markings, an identification tag, QR code printed paper or a barcode becomes illegible, or if there are a plurality of cables with the identical or similar information, much time is consumed to identify the specific cable.
Further, if the other active optical fiber cable than the specific optical fiber cable to be removed is cut by mistake, the interruption of optical signals in the other active optical fiber cable for proper operation of terminating equipment and transmission of information may cause serious accidents.